1. Field of the Invention
The present invention relates to a method and a circuit arrangement for independent operation of a plurality of visual display units from one screen control unit.
2. Description of the Related Art
In equipment whose control system is based on PC (person computer) technology, a visual display unit is in general operated from a monitor interface which operates, for example, on the VGA Standard and is provided by a special screen control unit which in the example is a so-called VGA controller. The PC software operating system includes an appropriate driver program. If the intention is to connect a plurality of visual display units which are intended to indicate different information at the same time, a dedicated screen control unit is required for each visual display unit.
A plurality of visual display units are in general required wherever a number of people are monitoring data acquisition or processing processes or where different people are each intended to have access to only a part of the overall information. This is the situation, for example, with cash registers or with service terminals which are equipped at least with an operator display and a customer display. In addition, an animation screen is frequently provided for displaying advertising or general information, or else a numerical display device for displaying the reservation number of a next customers To provide a screen control unit for each display unit consumes space and is expensive, as well as having a disadvantageous effect on the processing speed of the PC.
In U.S. Pat. No. 4 965 559, it has therefore been proposed for a plurality of visual display units to be operated from one screen control unit, which emits clock signals and a number of character-related or pixel-related video data signals corresponding to the line and column resolution of a two-dimensional rectangular raster image. In this case, the clock and video data signals which belong to rectangular subareas of the raster image are in each case supplied to a visual display unit. However, in addition, an individual assignment or matching device (look-up table) is required for each visual display unit.